The following vehicle has hitherto been well known. That is, the vehicle has installed thereon a motor generator having a power generation function and an engine start function, and a starter configured to crank an engine when the engine is started. The vehicle further has an idle stop function of automatically stopping the engine in accordance with set conditions, and restarting the engine in accordance with a request for restarting.
In this type of vehicle, the motor generator, which is operationally associated with the engine, is used to convert an engine output to generated power, and the motor generator and the starter are selectively or simultaneously used to start the engine depending on a state (e.g., refer to Patent Literatures 1 and 2).
Specifically, a battery is charged by the motor generator through a rotation output of the engine in a normal operation, and when the engine is started, a starting torque and a driving torque are respectively supplied to the motor generator and the starter through a battery output.
For example, the engine start control device disclosed in Patent Literature 1 includes control means for starting the engine using the starter when the engine is initially started through an ignition key, and restarting the engine using the motor generator when the engine is restarted from an engine stop state brought about by the idle stop function.
Moreover, the engine start control device disclosed in Patent Literature 1 also includes control means for starting the engine using the starter at a temperature less than a predetermined temperature, and starting the engine using the motor generator at a temperature equal to or more than the predetermined temperature, based on an ambient temperature of the engine.
Further, the engine start control device disclosed in Patent Literature 2 includes the following control means. Specifically, the engine start control device disclosed in Patent Literature 2 is configured to perform cranking using only the starter or simultaneously using the starter and the motor generator at the beginning of the cranking when the stopped engine is to be started.
Further, the engine start control device disclosed in Patent Literature 2 is configured to set a period of cranking by the starter or a rotation speed at which the cranking is finished in accordance with a friction resistance of a crankshaft, and then transition to cranking by only the motor generator.